This invention pertains to apnea event devices utilized to detect the cessation of breathing in an in vivo respiratory system, and to methods of operating respirating gas supply apparatus so that apnea events caused by the occlusion of upper airway passages in the in vivo respiratory system are remedied.
U.S. patent application Ser. No. 210,653, filed Nov. 26, 1980 and now U.S. Pat. No. 4,414,982 by Gerald P. Durkan and commonly assigned herewith, is incorporated herein by reference as disclosing a respirator apparatus including a predominately fluidically operated apnea event circuit which signals the occurrence of an apnea event after the lapse of a predetermined time interval since the last inspiration attempted by an in vivo respiratory system. One cause of apnea events such as those detected by the apparatus of U.S. patent application Ser. No. 210,653 is the occlusion of upper airways, such as the oropharyngeal airway, in the invivo respiratory system.
In the above respect, it has been suggested by Remmers et al. ("Pathogenesis of Upper Airway Occlusion During Sleep", Journal of Applied Physiology 1978; 44:931-38) that in some in vivo respiratory systems the subatmospheric or negative pressure occasioned during inspiration sucks the tongue and soft palate against the posterior oropharyngeal wall. Other causes and conditions associated with upper airway obstruction/occlusion are summarized by Sullivan et al. ("Reversal of Obstructive Sleep Apnoea By Continuous Positive Airway Pressure Applied Through the Nares", The Lancet, Apr. 18, 1981, pp. 862-865) which is incorporated herein by reference for a discussion of the obstruction/occlusion phenomena. Sullivan et al. report treatments for obstructive sleep apnoea syndrome wherein low levels of pressure (in the range of 4.5 to 10 cm water) were continuously applied to provide a pneumatic splint for the nasopharyngeal airway.
U.S. Pat. No. 4,155,356 to Venegas discloses a respiration assisting method and apparatus comprising means for generating a series of pressure pulses and means for transmitting the pressure pulses to air passageways in the lungs. The transmission means comprises a tube placed in the trachea so that pressure waves created by the pressure pulses outwardly displace walls of collapsed air passageways in the lungs and maintain such outward displacement during expiration. Venegas provides no means for the sensing of conditions in the lungs nor does he coordinate the application of pressure pulses in time relation with the occurrence of such conditions.
In view of the foregoing, it is an object of this invention to provide a respirating gas supply apparatus which, upon the detection of an appropriate apnea event caused by the occlusion or obstruction of upper airway passages in an in vivo respiratory system, attempts to remedy the occlusion or obstruction in the upper airway passages.